/*
 * @(#)AbstractMap.java	1.42 04/02/19
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package com.lab.util.collection;

/*
 * @(#)AbstractMap.java	1.42 04/02/19
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

import java.util.AbstractCollection;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public abstract class AbstractMap<K, V> implements Map<K, V> {
	/**
	 * Sole constructor.  (For invocation by subclass constructors, typically
	 * implicit.)
	 */
	protected AbstractMap() {}

	// Query Operations

	/**
	 * Returns the number of key-value mappings in this map.  If the map
	 * contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
	 * <tt>Integer.MAX_VALUE</tt>.<p>
	 *
	 * This implementation returns <tt>entrySet().size()</tt>.
	 *
	 * @return the number of key-value mappings in this map.
	 */
	public int size() {
		return entrySet().size();
	}

	/**
	 * Returns <tt>true</tt> if this map contains no key-value mappings. <p>
	 *
	 * This implementation returns <tt>size() == 0</tt>.
	 *
	 * @return <tt>true</tt> if this map contains no key-value mappings.
	 */
	public boolean isEmpty() {
		return size() == 0;
	}

	/**
	 * Returns <tt>true</tt> if this map maps one or more keys to this value.
	 * More formally, returns <tt>true</tt> if and only if this map contains
	 * at least one mapping to a value <tt>v</tt> such that <tt>(value==null ?
	 * v==null : value.equals(v))</tt>.  This operation will probably require
	 * time linear in the map size for most implementations of map.<p>
	 *
	 * This implementation iterates over entrySet() searching for an entry
	 * with the specified value.  If such an entry is found, <tt>true</tt> is
	 * returned.  If the iteration terminates without finding such an entry,
	 * <tt>false</tt> is returned.  Note that this implementation requires
	 * linear time in the size of the map.
	 *
	 * @param value value whose presence in this map is to be tested.
	 * 
	 * @return <tt>true</tt> if this map maps one or more keys to this value.
	 */
	public boolean containsValue(Object value) {
		Iterator<Entry<K, V>> i = entrySet().iterator();
		if (value == null) {
			while (i.hasNext()) {
				Entry<K, V> e = i.next();
				if (e.getValue() == null) {
					return true;
				}
			}
		} else {
			while (i.hasNext()) {
				Entry<K, V> e = i.next();
				if (value.equals(e.getValue())) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Returns <tt>true</tt> if this map contains a mapping for the specified
	 * key. <p>
	 *
	 * This implementation iterates over <tt>entrySet()</tt> searching for an
	 * entry with the specified key.  If such an entry is found, <tt>true</tt>
	 * is returned.  If the iteration terminates without finding such an
	 * entry, <tt>false</tt> is returned.  Note that this implementation
	 * requires linear time in the size of the map; many implementations will
	 * override this method.
	 *
	 * @param key key whose presence in this map is to be tested.
	 * @return <tt>true</tt> if this map contains a mapping for the specified
	 *            key.
	 * 
	 * @throws NullPointerException if the key is <tt>null</tt> and this map
	 *            does not permit <tt>null</tt> keys.
	 */
	public boolean containsKey(Object key) {
		Iterator<Map.Entry<K, V>> i = entrySet().iterator();
		if (key == null) {
			while (i.hasNext()) {
				Entry<K, V> e = i.next();
				if (e.getKey() == null) {
					return true;
				}
			}
		} else {
			while (i.hasNext()) {
				Entry<K, V> e = i.next();
				if (key.equals(e.getKey())) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Returns the value to which this map maps the specified key.  Returns
	 * <tt>null</tt> if the map contains no mapping for this key.  A return
	 * value of <tt>null</tt> does not <i>necessarily</i> indicate that the
	 * map contains no mapping for the key; it's also possible that the map
	 * explicitly maps the key to <tt>null</tt>.  The containsKey operation
	 * may be used to distinguish these two cases. <p>
	 *
	 * This implementation iterates over <tt>entrySet()</tt> searching for an
	 * entry with the specified key.  If such an entry is found, the entry's
	 * value is returned.  If the iteration terminates without finding such an
	 * entry, <tt>null</tt> is returned.  Note that this implementation
	 * requires linear time in the size of the map; many implementations will
	 * override this method.
	 *
	 * @param key key whose associated value is to be returned.
	 * @return the value to which this map maps the specified key.
	 * 
	 * @throws NullPointerException if the key is <tt>null</tt> and this map
	 *		  does not permit <tt>null</tt> keys.
	 * 
	 * @see #containsKey(Object)
	 */
	public V get(Object key) {
		Iterator<Entry<K, V>> i = entrySet().iterator();
		if (key == null) {
			while (i.hasNext()) {
				Entry<K, V> e = i.next();
				if (e.getKey() == null) {
					return e.getValue();
				}
			}
		} else {
			while (i.hasNext()) {
				Entry<K, V> e = i.next();
				if (key.equals(e.getKey())) {
					return e.getValue();
				}
			}
		}
		return null;
	}

	// Modification Operations

	/**
	 * Associates the specified value with the specified key in this map
	 * (optional operation).  If the map previously contained a mapping for
	 * this key, the old value is replaced.<p>
	 *
	 * This implementation always throws an
	 * <tt>UnsupportedOperationException</tt>.
	 *
	 * @param key key with which the specified value is to be associated.
	 * @param value value to be associated with the specified key.
	 * 
	 * @return previous value associated with specified key, or <tt>null</tt>
	 *	       if there was no mapping for key.  (A <tt>null</tt> return can
	 *	       also indicate that the map previously associated <tt>null</tt>
	 *	       with the specified key, if the implementation supports
	 *	       <tt>null</tt> values.)
	 * 
	 * @throws UnsupportedOperationException if the <tt>put</tt> operation is
	 *	          not supported by this map.
	 * 
	 * @throws ClassCastException if the class of the specified key or value
	 * 	          prevents it from being stored in this map.
	 * 
	 * @throws IllegalArgumentException if some aspect of this key or value *
	 *            prevents it from being stored in this map.
	 * 
	 * @throws NullPointerException if this map does not permit <tt>null</tt>
	 *            keys or values, and the specified key or value is
	 *            <tt>null</tt>.
	 */
	public V put(K key, V value) {
		throw new UnsupportedOperationException();
	}

	/**
	 * Removes the mapping for this key from this map if present (optional
	 * operation). <p>
	 *
	 * This implementation iterates over <tt>entrySet()</tt> searching for an
	 * entry with the specified key.  If such an entry is found, its value is
	 * obtained with its <tt>getValue</tt> operation, the entry is removed
	 * from the Collection (and the backing map) with the iterator's
	 * <tt>remove</tt> operation, and the saved value is returned.  If the
	 * iteration terminates without finding such an entry, <tt>null</tt> is
	 * returned.  Note that this implementation requires linear time in the
	 * size of the map; many implementations will override this method.<p>
	 *
	 * Note that this implementation throws an
	 * <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> iterator
	 * does not support the <tt>remove</tt> method and this map contains a
	 * mapping for the specified key.
	 *
	 * @param key key whose mapping is to be removed from the map.
	 * @return previous value associated with specified key, or <tt>null</tt>
	 *	       if there was no entry for key.  (A <tt>null</tt> return can
	 *	       also indicate that the map previously associated <tt>null</tt>
	 *	       with the specified key, if the implementation supports
	 *	       <tt>null</tt> values.)
	 * @throws UnsupportedOperationException if the <tt>remove</tt> operation
	 * 		  is not supported by this map.
	 */
	public V remove(Object key) {
		Iterator<Entry<K, V>> i = entrySet().iterator();
		Entry<K, V> correctEntry = null;
		if (key == null) {
			while (correctEntry == null && i.hasNext()) {
				Entry<K, V> e = i.next();
				if (e.getKey() == null) {
					correctEntry = e;
				}
			}
		} else {
			while (correctEntry == null && i.hasNext()) {
				Entry<K, V> e = i.next();
				if (key.equals(e.getKey())) {
					correctEntry = e;
				}
			}
		}

		V oldValue = null;
		if (correctEntry != null) {
			oldValue = correctEntry.getValue();
			i.remove();
		}
		return oldValue;
	}

	// Bulk Operations

	/**
	 * Copies all of the mappings from the specified map to this map
	 * (optional operation).  These mappings will replace any mappings that
	 * this map had for any of the keys currently in the specified map.<p>
	 *
	 * This implementation iterates over the specified map's
	 * <tt>entrySet()</tt> collection, and calls this map's <tt>put</tt>
	 * operation once for each entry returned by the iteration.<p>
	 *
	 * Note that this implementation throws an
	 * <tt>UnsupportedOperationException</tt> if this map does not support
	 * the <tt>put</tt> operation and the specified map is nonempty.
	 *
	 * @param t mappings to be stored in this map.
	 * 
	 * @throws UnsupportedOperationException if the <tt>putAll</tt> operation
	 * 		  is not supported by this map.
	 * 
	 * @throws ClassCastException if the class of a key or value in the
	 * 	          specified map prevents it from being stored in this map.
	 * 
	 * @throws IllegalArgumentException if some aspect of a key or value in
	 *	          the specified map prevents it from being stored in this map.
	 * @throws NullPointerException if the specified map is <tt>null</tt>, or if
	 *         this map does not permit <tt>null</tt> keys or values, and the
	 *         specified map contains <tt>null</tt> keys or values.
	 */
	public void putAll(Map<? extends K, ? extends V> t) {
		Iterator<? extends Entry<? extends K, ? extends V>> i = t.entrySet()
				.iterator();
		while (i.hasNext()) {
			Entry<? extends K, ? extends V> e = i.next();
			put(e.getKey(), e.getValue());
		}
	}

	/**
	 * Removes all mappings from this map (optional operation). <p>
	 *
	 * This implementation calls <tt>entrySet().clear()</tt>.
	 *
	 * Note that this implementation throws an
	 * <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt>
	 * does not support the <tt>clear</tt> operation.
	 *
	 * @throws    UnsupportedOperationException clear is not supported
	 * 		  by this map.
	 */
	public void clear() {
		entrySet().clear();
	}

	// Views

	/**
	 * Each of these fields are initialized to contain an instance of the
	 * appropriate view the first time this view is requested.  The views are
	 * stateless, so there's no reason to create more than one of each.
	 */
	transient volatile Set<K> keySet = null;
	transient volatile Collection<V> values = null;

	/**
	 * Returns a Set view of the keys contained in this map.  The Set is
	 * backed by the map, so changes to the map are reflected in the Set,
	 * and vice-versa.  (If the map is modified while an iteration over
	 * the Set is in progress, the results of the iteration are undefined.)
	 * The Set supports element removal, which removes the corresponding entry
	 * from the map, via the Iterator.remove, Set.remove,  removeAll
	 * retainAll, and clear operations.  It does not support the add or
	 * addAll operations.<p>
	 *
	 * This implementation returns a Set that subclasses
	 * AbstractSet.  The subclass's iterator method returns a "wrapper
	 * object" over this map's entrySet() iterator.  The size method delegates
	 * to this map's size method and the contains method delegates to this
	 * map's containsKey method.<p>
	 *
	 * The Set is created the first time this method is called,
	 * and returned in response to all subsequent calls.  No synchronization
	 * is performed, so there is a slight chance that multiple calls to this
	 * method will not all return the same Set.
	 *
	 * @return a Set view of the keys contained in this map.
	 */
	public Set<K> keySet() {
		if (keySet == null) {
			keySet = new AbstractSet<K>() {
				@Override
				public Iterator<K> iterator() {
					return new Iterator<K>() {
						private Iterator<Entry<K, V>> i = entrySet().iterator();

						public boolean hasNext() {
							return i.hasNext();
						}

						public K next() {
							return i.next().getKey();
						}

						public void remove() {
							i.remove();
						}
					};
				}

				@Override
				public int size() {
					return AbstractMap.this.size();
				}

				@Override
				public boolean contains(Object k) {
					return AbstractMap.this.containsKey(k);
				}
			};
		}
		return keySet;
	}

	/**
	 * Returns a collection view of the values contained in this map.  The
	 * collection is backed by the map, so changes to the map are reflected in
	 * the collection, and vice-versa.  (If the map is modified while an
	 * iteration over the collection is in progress, the results of the
	 * iteration are undefined.)  The collection supports element removal,
	 * which removes the corresponding entry from the map, via the
	 * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
	 * <tt>removeAll</tt>, <tt>retainAll</tt> and <tt>clear</tt> operations.
	 * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.<p>
	 *
	 * This implementation returns a collection that subclasses abstract
	 * collection.  The subclass's iterator method returns a "wrapper object"
	 * over this map's <tt>entrySet()</tt> iterator.  The size method
	 * delegates to this map's size method and the contains method delegates
	 * to this map's containsValue method.<p>
	 *
	 * The collection is created the first time this method is called, and
	 * returned in response to all subsequent calls.  No synchronization is
	 * performed, so there is a slight chance that multiple calls to this
	 * method will not all return the same Collection.
	 *
	 * @return a collection view of the values contained in this map.
	 */
	public Collection<V> values() {
		if (values == null) {
			values = new AbstractCollection<V>() {
				@Override
				public Iterator<V> iterator() {
					return new Iterator<V>() {
						private Iterator<Entry<K, V>> i = entrySet().iterator();

						public boolean hasNext() {
							return i.hasNext();
						}

						public V next() {
							return i.next().getValue();
						}

						public void remove() {
							i.remove();
						}
					};
				}

				@Override
				public int size() {
					return AbstractMap.this.size();
				}

				@Override
				public boolean contains(Object v) {
					return AbstractMap.this.containsValue(v);
				}
			};
		}
		return values;
	}

	/**
	 * Returns a set view of the mappings contained in this map.  Each element
	 * in this set is a Map.Entry.  The set is backed by the map, so changes
	 * to the map are reflected in the set, and vice-versa.  (If the map is
	 * modified while an iteration over the set is in progress, the results of
	 * the iteration are undefined.)  The set supports element removal, which
	 * removes the corresponding entry from the map, via the
	 * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>,
	 * <tt>retainAll</tt> and <tt>clear</tt> operations.  It does not support
	 * the <tt>add</tt> or <tt>addAll</tt> operations.
	 *
	 * @return a set view of the mappings contained in this map.
	 */
	public abstract Set<Entry<K, V>> entrySet();

	// Comparison and hashing

	/**
	 * Compares the specified object with this map for equality.  Returns
	 * <tt>true</tt> if the given object is also a map and the two maps
	 * represent the same mappings.  More formally, two maps <tt>t1</tt> and
	 * <tt>t2</tt> represent the same mappings if
	 * <tt>t1.keySet().equals(t2.keySet())</tt> and for every key <tt>k</tt>
	 * in <tt>t1.keySet()</tt>, <tt> (t1.get(k)==null ? t2.get(k)==null :
	 * t1.get(k).equals(t2.get(k))) </tt>.  This ensures that the
	 * <tt>equals</tt> method works properly across different implementations
	 * of the map interface.<p>
	 *
	 * This implementation first checks if the specified object is this map;
	 * if so it returns <tt>true</tt>.  Then, it checks if the specified
	 * object is a map whose size is identical to the size of this set; if
	 * not, it returns <tt>false</tt>.  If so, it iterates over this map's
	 * <tt>entrySet</tt> collection, and checks that the specified map
	 * contains each mapping that this map contains.  If the specified map
	 * fails to contain such a mapping, <tt>false</tt> is returned.  If the
	 * iteration completes, <tt>true</tt> is returned.
	 *
	 * @param o object to be compared for equality with this map.
	 * @return <tt>true</tt> if the specified object is equal to this map.
	 */
	@Override
	public boolean equals(Object o) {
		if (o == this) {
			return true;
		}

		if (!(o instanceof Map)) {
			return false;
		}
		Map<K, V> t = (Map<K, V>) o;
		if (t.size() != size()) {
			return false;
		}

		try {
			Iterator<Entry<K, V>> i = entrySet().iterator();
			while (i.hasNext()) {
				Entry<K, V> e = i.next();
				K key = e.getKey();
				V value = e.getValue();
				if (value == null) {
					if (!(t.get(key) == null && t.containsKey(key))) {
						return false;
					}
				} else {
					if (!value.equals(t.get(key))) {
						return false;
					}
				}
			}
		} catch (ClassCastException unused) {
			return false;
		} catch (NullPointerException unused) {
			return false;
		}

		return true;
	}

	/**
	 * Returns the hash code value for this map.  The hash code of a map is
	 * defined to be the sum of the hash codes of each entry in the map's
	 * <tt>entrySet()</tt> view.  This ensures that <tt>t1.equals(t2)</tt>
	 * implies that <tt>t1.hashCode()==t2.hashCode()</tt> for any two maps
	 * <tt>t1</tt> and <tt>t2</tt>, as required by the general contract of
	 * Object.hashCode.<p>
	 *
	 * This implementation iterates over <tt>entrySet()</tt>, calling
	 * <tt>hashCode</tt> on each element (entry) in the Collection, and adding
	 * up the results.
	 *
	 * @return the hash code value for this map.
	 * @see Map.Entry#hashCode()
	 * @see Object#hashCode()
	 * @see Object#equals(Object)
	 * @see Set#equals(Object)
	 */
	@Override
	public int hashCode() {
		int h = 0;
		Iterator<Entry<K, V>> i = entrySet().iterator();
		while (i.hasNext()) {
			h += i.next().hashCode();
		}
		return h;
	}

	/**
	 * Returns a string representation of this map.  The string representation
	 * consists of a list of key-value mappings in the order returned by the
	 * map's <tt>entrySet</tt> view's iterator, enclosed in braces
	 * (<tt>"{}"</tt>).  Adjacent mappings are separated by the characters
	 * <tt>", "</tt> (comma and space).  Each key-value mapping is rendered as
	 * the key followed by an equals sign (<tt>"="</tt>) followed by the
	 * associated value.  Keys and values are converted to strings as by
	 * <tt>String.valueOf(Object)</tt>.<p>
	 *
	 * This implementation creates an empty string buffer, appends a left
	 * brace, and iterates over the map's <tt>entrySet</tt> view, appending
	 * the string representation of each <tt>map.entry</tt> in turn.  After
	 * appending each entry except the last, the string <tt>", "</tt> is
	 * appended.  Finally a right brace is appended.  A string is obtained
	 * from the stringbuffer, and returned.
	 *
	 * @return a String representation of this map.
	 */
	@Override
	public String toString() {
		StringBuffer buf = new StringBuffer();
		buf.append("{");

		Iterator<Entry<K, V>> i = entrySet().iterator();
		boolean hasNext = i.hasNext();
		while (hasNext) {
			Entry<K, V> e = i.next();
			K key = e.getKey();
			V value = e.getValue();
			if (key == this) {
				buf.append("(this Map)");
			} else {
				buf.append(key);
			}
			buf.append("=");
			if (value == this) {
				buf.append("(this Map)");
			} else {
				buf.append(value);
			}
			hasNext = i.hasNext();
			if (hasNext) {
				buf.append(", ");
			}
		}

		buf.append("}");
		return buf.toString();
	}

	/**
	 * Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys
	 * and values themselves are not cloned.
	 *
	 * @return a shallow copy of this map.
	 */
	@Override
	protected Object clone() throws CloneNotSupportedException {
		AbstractMap<K, V> result = (AbstractMap<K, V>) super.clone();
		result.keySet = null;
		result.values = null;
		return result;
	}

	/**
	 * This should be made public as soon as possible.  It greatly simplifies
	 * the task of implementing Map.
	 */
	static class SimpleEntry<K, V> implements Entry<K, V> {
		K key;
		V value;

		public SimpleEntry(K key, V value) {
			this.key = key;
			this.value = value;
		}

		public SimpleEntry(Entry<K, V> e) {
			this.key = e.getKey();
			this.value = e.getValue();
		}

		public K getKey() {
			return key;
		}

		public V getValue() {
			return value;
		}

		public V setValue(V value) {
			V oldValue = this.value;
			this.value = value;
			return oldValue;
		}

		@Override
		public boolean equals(Object o) {
			if (!(o instanceof Map.Entry)) {
				return false;
			}
			Map.Entry e = (Map.Entry) o;
			return eq(key, e.getKey()) && eq(value, e.getValue());
		}

		@Override
		public int hashCode() {
			return (key == null ? 0 : key.hashCode())
					^ (value == null ? 0 : value.hashCode());
		}

		@Override
		public String toString() {
			return key + "=" + value;
		}

		private static boolean eq(Object o1, Object o2) {
			return o1 == null ? o2 == null : o1.equals(o2);
		}
	}
}
